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Systematic Reviews: Related Review Types

Related Review Types

There are dozens of different review types.  Many of them use parts of the systematic review process. 


Meta-analyses statistically combine the results of studies in a systematic review to provide a more precise effect of the results. Meta-analysis can only be done when all included studies are sufficiently similar. All studies must measure the same outcome in the same way at the same time intervals.

Scoping/Mapping Reviews

Scoping/Mapping reviews examine a broad topic rather than try to answer a specific question. They identify the nature and extent of existing research in order to:

  • identify gaps in the literature to see where future research is needed 
  • examine the extent, variety, and characteristics of the evidence on a topic 
  • determine if it's feasible to do a systematic review

Like systematic reviews, they require a comprehensive systematic search and structured reporting but they don't assess risk of bias of included studies.

Systematized Reviews

Systematized reviews only include some elements of the systematic review process. They're usually conducted as post-graduate student assignments in a short time frame. They may not include: 

  • systematic comprehensive searching
  • quality assessment of selected studies
  • a systematic synthesis of the results 

Mixed Methods Review

Mixed method reviews are systematic reviews that include both qualitative and quantitative studies. Unlike most systematic reviews which focus only on the effectiveness of an intervention, mixed methods reviews give decision-makers a more complete understanding of complex issues.  They are difficult to conduct because of the heterogeneous nature of the included studies. This complicates the searching, quality assessment, data extraction, and data synthesis. There are several methods of synthesizing the diverse types of studies. 

Umbrella Reviews

An umbrella review is a review of reviews. It compiles the evidence from existing reviews, usually systematic reviews and meta-analyses. Umbrella reviews often compare multiple different competing interventions for a condition.   

Rapid Reviews

Rapid reviews use systematic review methods but set limits on the process in order to complete the review as quickly as possible. They are usually used for emergency decision-making in critical situations such as the Ebola virus outbreak. In order to produce results quickly, they may limit the comprehensiveness of the search or the quality appraisal.  

Systematic Reviews of Case Reports/Series

Systematic reviews of case reports/series aren't frequently done but sometimes there is no other evidence on a rare disease, new drug, or adverse events. In these cases, you might only have case reports to examine.


  • Cochrane only gives snippets of advice:

Cochrane Handbook, Ch 24:

“for some rare or delayed adverse outcomes only case series or case-control studies may be available. Non-randomized studies of interventions with some study design features that are more susceptible to bias may be acceptable for evaluation of serious adverse events in the absence of better evidence, but the risk of bias must still be assessed and reported”

Cochrane Systematic Reviews of Adverse Effects: Framework for a Structured Approach. BMC Med Res Methodol. (2007) 7:32. doi: 10.1186/1471-2288-7-32

"The Cochrane Adverse Effects group has shown that case studies may be the best settings in which to observe adverse effects, especially when they are rare and acute."

Evaluation of quality of case reports:


Prospero accepts protocols for SRs of case reports